Scientists at Tel Aviv University and Rabin Medical Center have discovered they can detect lung cancer early in smokers by performing a CT scan at the time they are admitted as pneumonia patients. Often, the pneumonia is caused by young cancer cells blocking air pathways.
http://nocamels.com/2016/01/lung-cancer-early-detection-smoking-pneumonia/
http://www.amjmed.com/article/S0002-9343%2815%2901035-9/abstract